[Xignal]

SPOILER
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Enter via the Mine Tunnels from the Swamp, go north through the hub area, take the left corridor to the stairs, go up and search for a large, metal switch on a wall. Pull it to open the large red door blocking the way to the idol. Then either go back down the stairs, go back to the hub, and take the elevator up (found past Z'Ant); or jump down through the trapdoor (near the sword) and make your way back to the front entrance of the fort.